This application claims the priority and benefit of U.S. provisional patent application 61/218,107 filed Jun. 18, 2009, entitled “MME COORDINATED BACKHAUL HEADER COMPRESSION”, which is incorporated herein by reference in its entirety. This application is related to PCT/SE2008/051004 (WO/2009/134178), entitled “SELF-BACKHAULING IN LTE”, which is incorporated herein by reference.
This invention pertains to telecommunications, and particularly to header compression.
In a typical cellular radio system, wireless terminals (also known as mobile stations and/or user equipment units (UEs)) communicate via a radio access network (RAN) to one or more core networks. The radio access network (RAN) covers a geographical area which is divided into cell areas, with each cell area being served by a base station, e.g., a radio base station (RBS), which in some networks is also called a “NodeB”. A cell is a geographical area where radio coverage is provided by the radio base station equipment at a base station site. Each cell is identified by an identity within the local radio area, which is broadcast in the cell. The base stations communicate over the air interface operating on radio frequencies with the user equipment units (UE) within range of the base stations.
In some versions of the radio access network, several base stations are typically connected (e.g., by landlines or microwave) to a radio network controller (RNC). The radio network controller, also sometimes termed a base station controller (BSC), supervises and coordinates various activities of the plural base stations connected thereto. The radio network controllers are typically connected to one or more core networks.
The Universal Mobile Telecommunications System (UMTS) is a third generation mobile communication system, which evolved from the Global System for Mobile Communications (GSM), and is intended to provide improved mobile communication services based on Wideband Code Division Multiple Access (WCDMA) access technology. UTRAN is essentially a radio access network using wideband code division multiple access for user equipment units (UEs).
In a forum known as the Third Generation Partnership Project (3GPP), telecommunications suppliers propose and agree upon standards for third generation networks and UTRAN specifically, and investigate enhanced data rate and radio capacity. The Third Generation Partnership Project (3GPP) has undertaken to evolve further the UTRAN and GSM based radio access network technologies. Specifications for the Evolved Universal Terrestrial Radio Access Network (E-UTRAN) are ongoing within the 3rd Generation Partnership Project (3GPP). The Evolved Universal Terrestrial Radio Access Network (E-UTRAN) comprises the Long Term Evolution (LTE) and System Architecture Evolution (SAE).
Long Term Evolution (LTE) is a variant of a 3GPP radio access technology wherein the radio base station nodes are connected directly to a core network rather than to radio network controller (RNC) nodes. In general, in LTE the functions of a radio network controller (RNC) node are performed by the radio base stations nodes. As such, the radio access network (RAN) of an LTE system has an essentially “flat” architecture comprising radio base station nodes without reporting to radio network controller (RNC) nodes.
The evolved UTRAN (E-UTRAN) comprises evolved base station nodes, e.g., evolved NodeBs or eNodeBs or eNBs, providing evolved UTRA user-plane and control-plane protocol terminations toward the user equipment unit (UE). The eNB hosts the following functions (among other functions not listed): (1) functions for radio resource management (e.g., radio bearer control, radio admission control), connection mobility control, dynamic resource allocation (scheduling); (2) selection of a mobility management entity (MME) when no routing to an MME can be determined from the information provided by the user equipment unit (UE); and (3) User Plane functions, including IP Header Compression and encryption of user data streams; and switching of U-plane for support of UE mobility. The eNB hosts the PHYsical (PHY), Medium Access Control (MAC), Radio Link Control (RLC), and Packet Data Control Protocol (PDCP) layers that include the functionality of user-plane header-compression and encryption. The eNodeB also offers Radio Resource Control (RRC) functionality corresponding to the control plane. The eNodeB performs many functions including radio resource management, admission control, scheduling, enforcement of negotiated UL QoS, cell information broadcast, ciphering/deciphering of user and control plane data, and compression/decompression of DL/UL user plane packet headers.
The aforementioned mobility management entity (MME) is the main signaling node/entity in the Evolved Packet Core (EPC). The mobility management entity is responsible for initiating paging and authentication of the wireless terminal (UE). The mobility management entity also keeps location information at the Tracking Area level for idle mode UEs and is involved in choosing the right gateway during the initial registration process. The MME connects to eNBs through the S1-MME interface and connects to a serving gateway (SGW) through the S11 interface. Multiple MMEs can be grouped together in a pool to meet increasing signaling load in the network. The MME also plays an important part in handover signaling between LTE and 2G/3G networks.
The Evolved Packet Core is the IP-based core network defined by 3GPP in release 8 for use by LTE and other access technologies. The EPC typically includes a Mobility Management Entity, a Serving Gateway and PDN Gateway subcomponents. The EPC provides a simplified, all-IP core network architecture to give access to various services such as the ones provided in IMS (IP Multimedia Subsystem).
GPRS Tunnelling Protocol (GTP) is a group of IP-based communications protocols used to establish and manage communication sessions and carry encapsulated user data packets in General Packet Radio Service (GPRS) within GSM and UMTS networks, as well as in SAE/LTE networks.
In WCDMA networks, user plane ciphering and header compression (HC) is performed in the radio network controller node (RNC). This means that the traffic between the NodeBs and the RNC is effectively header compressed, leading to reduced traffic over the expensive RAN backhaul (transport between NodeB and RNC). However, in LTE the header compression is performed in the eNodeB. This means that upstream backhaul links (extending between the eNodeB and the evolved core network) carry user IP packets without header compression. Transporting IP packets on the upstream backhaul link without header compression presents significant overhead. For example, with an average packet size of 500 bytes, a compressed TCP/IP header removes 40 bytes of the packet, resulting in 8% of traffic reduction at no loss of functions. If typical packet sizes are smaller, the gain can be higher.